In a display device such as a thin television represented by a liquid crystal display, a reflection type and a transmission type are known. Conventionally, a film of pure aluminum having a high reflectance has been adopted as a reflection-type display device. However, if this pure aluminum is used as a reflective film, in a case where the reflective film is bonded to a transparent electrode such as ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide) (hereinafter occasionally referred to as transparent electrode layer), an electrolytic corrosion phenomenon is caused due to an electrical chemical reaction when the patterning of the reflective film is carried out. This causes a formation of a circuit fulfilling a practical characteristics to be difficult.
For this reason, Ag or Ag-based alloy which has a high reflectance and is resistant to an electrical chemical corrosion was adopted as material for the reflective film, instead of pure aluminum (Patent Publication 1). However, it was pointed out that it is difficult to form a desired circuit due to an influence of its etching characteristics if aluminum base alloy is used as reflective film material, so that the productivity tends to become inferior.
Such being the case, aluminum base alloy which restrains such an electrolytic corrosion phenomenon upon the patterning was proposed (Patent Publication 2). However, as to the film formed with the aluminum base alloy disclosed in this publication, neither the reflectance characteristics nor the electrical characteristics upon bonding has not been cleared yet. In addition, although Al-based material which attains the direct bonding thereof to the transparent electrode layer such as ITO was proposed (Patent Publications 3 and 4), the reflectance characteristics of the film formed with the aluminum base material disclosed in these publications has not been studied, so that whether or not it is provided with a practical reflectance characteristics has not been cleared yet.    Patent Publication 1: Japanese Patent No. 3302894    Patent Publication 2: International Publication WO97/13885    Patent Publication 3: Japanese Patent Laid-open Publication 2003-89864    Patent Publication 4: Japanese Patent Laid-open Publication 2004-214606